This application claims the benefit of U.S. Provisional Patent Application No. 60/317,138, filed on Sep. 6, 2001.
Traditionally, VCSEL dies are vertically mounted to a printed circuit board, or PCB, with light emitting from the same surface as the electrical contacts. The PCB is usually made of FR4 or ceramic. As shown in the prior art of FIG. 1, a TO can 12 has wire bonds 16 used in electrically connecting the VCSEL die 14. Wire bonds 16 are more susceptible to damage than solder bumps, and are generally avoided if possible. In addition, wire bonding is inconsistent in terms of variance in electrical properties. As the wire lengths vary, the resistance, inductance and capacitance also varies.
As shown in FIG. 1, the TO can's base comprises a header 20 and a conductive spacer 18. A metallic structure 22, referred to as a can, provides a hermetic seal for a VCSEL laser array 14. Optical signals 26 exit the TO can 10 through a lens 24, and may be appropriately coupled into a waveguide (not shown). Lensing mechanisms are often needed to couple light as desired into a waveguide or optical fiber. For example, a VCSEL laser die contains electrical contacts on the same surface of light emission, and wire bonding to that surface will increase the minimum distance from the active surface of the laser to the optical fiber. As a result, the signal may require lensing to gather diverging light.
A method of attaching the VCSEL die using metal to metal contacts on the pads such as solder bumps or stud bumps can make closer connections that are more consistent in electrical variance and offer greater structural stability than wire bonds. This method of attaching is commonly referred to as flip chipping. Wire bonding will add to the overall height in the package more so than flip chipping, as shown in FIG. 1. In addition, flip chipping allows for a waveguide and/or lens structure to be placed closer to the surface of light emission. Thus, more light could be gathered from an optical port into a waveguide or optical fiber. This in turn may preserve signal integrity. In this invention is provided a novel way to couple light from an optical device, into a waveguide, and subsequently into an optical fiber. The invention may allow coupling of a more uniform optical beam profile while transmitting an appropriate optical energy amount to a receiving device. In addition, the invention may promote signal integrity.